The goal of the Hybridoma Facility is to produce monoclonal antibodies (MAbs) for use in characterizing, detecting, and purifying tumor antigens and other cancer-related proteins. The Facility generates MAbs primarily by fusing the spleens of antigen-immunized mice with a myeloma-derived fusion partner to immortalize antigen-specific antibodysecreting cells (hybridomas). The advantage of this approach is that it exploits the ability of the immune system of an intact animal to generate antibodies that react with antigens with high affinity, which can be used in a variety of applications that require the antibody to interact with target antigens with high specificity and sensitivity. Investigators often provide the facility with highly immunogenic glutathione-S-transferase (GST) fusion proteins, which in almost all cases generate a useful IgG-secreting MAb that recognizes the target antigen. In the most recent funding period, the Facility produced three classes of MAbs: 1)MAbs that recognize transcription factors and transcription factor domains for use in studies of cellular processes of oncogenesis;2) MAbs against molecules involved in RNA editing by microRNAs, which have emerged as crucial regulators of gene expression;and 3) antiidiotypic MAbs for use in cancer therapy. The facility has thus provided unique reagents to multiple Cancer Center members that have advanced their abilities to perform cutting edge research into underlying mechanisms of, and therapeutic approaches to cancer. In the most recent funding period the facility introduced hollow fiber bioreactors to enhance its capacity to produce large quantities of MAbs, and is beginning to perform custom-labeling of antibodies with fluorochromes and other tags to meet the increasing needs of investigators for labeled reagents for use in flow cytometry and other analysis systems. Another area being developed is the generation of human MAbs, using new methods combining flow cytometry, B cell activation via toll-like receptor ligands and immortalization with Epstein Barr virus. This technology provides the potential to develop reagents that can be used to treat human cancers and bypass problems with anti-mouse immune responses that develop in patients treated with mouse MAbs. This technology also offers the opportunity to analyze human B cell responses that may develop in disease states such as cancer.